How to know the difference between implantation bleeding and period

Medically Reviewed By Carolyn Kay, M.D.

— Written By Chaunie Brusie

Updated on May 27, 2022

It can be hard to tell the difference between implantation bleeding and menstruation, but there are a few key differences. For instance, implantation bleeding is usually lighter and occurs a few days before your period is due. This article explains how to tell the difference between implantation bleeding and menstruation. It also provides information about when implantation bleeding occurs and when you should contact a doctor.

What is implantation bleeding?

Implantation bleeding is a type of bleeding that can occur when a fertilized egg implants into the uterus. The uterus is full of blood vessels, which can break slightly as the egg implants. The bleeding that can occur will come out of the vagina, just like with a period.

Bleeding occurs in the first trimester in around 15–25% of pregnancies. If you are trying to conceive and do not have implantation bleeding, it does not mean that you are not pregnant. It is very possible to not have implantation bleeding even if you are pregnant.

What does implantation bleeding look like? 

Implantation bleeding can look just like the start of a menstrual period. It will most likely resemble a light spotting but can be anywhere from light pink to bright red. A brownish tinge can also be typical. Learn more here.

Implantation bleeding will usually not be as heavy as the heaviest day of your period. However, everyone is different, so implantation bleeding can look different for everyone. For instance, some people could have very light spotting, while others could have implantation bleeding that looks more like the first day of their period.

The blood from implantation bleeding can be so similar to menstrual blood that you may not be able to tell the difference right away. However, there may be other early signs of pregnancy that could signal that you are experiencing implantation bleeding.

Learn more about the different causes of vaginal bleeding here.

Are there any other early pregnancy symptoms with implantation bleeding? 

One of the ways you may be able to determine if you are experiencing implantation bleeding is to look for other early pregnancy symptoms. 

Once a fertilized egg implants in the uterus, the tissue that will become the placenta begins to produce the pregnancy hormone human chorionic gonadotropin (hCG). 

hCG is the hormone that is responsible for many of the signs of early pregnancy, such as: 

• breast tenderness
• nausea and vomiting
• fatigue
• sensitivity to smells

The rate of hCG doubles nearly every 2 days after implantation occurs, so it is possible to experience some of the early symptoms of pregnancy soon after implantation. 

However, some of the early signs of pregnancy may also be similar to those that people can experience before their period, so it may be difficult to tell if you really are pregnant. For instance, some people may even feel light cramping with implantation, which can be very similar to a period beginning. 

The best way to tell if you are pregnant is to wait to take a pregnancy test until you are due or even late for your period. 

Find out more about what to expect during the first month of pregnancy here.

When does implantation bleeding occur?

The very earliest that implantation could occur is 6 days after ovulation. On average, implantation can take place anywhere from 6–12 days after ovulation. 

Ovulation occurs at different times for every person, but, in general, it occurs somewhere around day 14 of the menstrual cycle. Ovulation is the process in which an egg is released from the ovary. Once the egg has been released, it can only live for 24 hours. 

Fertilization can take place if there are sperm waiting in the reproductive tract or if sperm is introduced within 24 hours of the egg being released. Sperm can live for up to 5 days once inside a female body. If fertilization occurs, the egg will then travel to the uterus, where it will implant. 

If ovulation occurs on day 14 and the egg is fertilized right away, the earliest that implantation could happen is on day 20. This is approximately 1 week before someone’s period would be due on a 28-day cycle. 

How long does implantation bleeding last?

Not everyone who is pregnant will experience implantation bleeding. If implantation bleeding does occur, it will likely only happen when or shortly after the egg implants into the uterus. 

Implantation bleeding may be as short as just one instance of someone experiencing blood when using the bathroom to light spotting that lasts 1–2 days. Implantation bleeding will generally not last more than 1–2 days. 

How common is implantation bleeding?

Not everyone will experience implantation bleeding, but some form of bleeding is common in early pregnancy.

Up to 25% of pregnancies will have some kind of bleeding in the early days and weeks, some of which can be implantation bleeding and some which may have other causes. 

Some bleeding during early pregnancy can happen, so if you do get a positive pregnancy test but experience bleeding, it does not mean that something is wrong. 

However, you should contact a doctor if you are experiencing continued bleeding and have received a positive pregnancy test. In some situations, there are common reasons for bleeding during early pregnancy, such as small hemorrhages or broken blood vessels. 

In other cases, continued and worsened bleeding may indicate that a miscarriage is occurring. It can take several weeks for hCG levels to lower, even with a miscarriage, so it is not always reliable to go by what a pregnancy test says. 

Bleeding during early pregnancy could also be a sign of an ectopic pregnancy, which can be life threatening. 

You should contact a doctor if you experience any of the following symptoms: 

• pain, especially pain that gets worse
• fever
• shortness of breath
• dizziness or weakness
• severe bleeding

Summary

Implantation bleeding can resemble the start of a menstrual period, but if you are trying to tell the difference between implantation bleeding and a period, there are a few things to look out for.

For example, implantation bleeding is generally lighter than a period and occurs up to 1 week before someone’s period might be due. Implantation bleeding may also happen before the start of early pregnancy symptoms, such as breast tenderness, fatigue, or morning sickness.

Some sort of bleeding can be expected in around 25% of pregnancies. However, if you are experiencing severe bleeding, pain, shortness of breath, or fever, you should contact a doctor immediately. 

How do you tell if it's your period or implantation bleeding?

Can implantation bleeding feel just like a period?

What implantation bleeding looks like?